class Meter(object):
    def __init__(self,value=0.0):
        self.value = float(value)
    def __get__(self, instance, owner):
        return self.value
    def __set__(self, instance, value):
        self.value = float(value)

class Foot(object):
    def __get__(self, instance, owner):
        return instance.meter * 3.2808
    def __set__(self, instance, value):
        instance.meter = float(value) / 3.2808

class Distance(object):
    meter = Meter()
    foot  = Foot()

if __name__ == '__main__':
    d = Distance()
    print(d.meter,d.foot)
    d.meter = 1
    print(d.meter,d.foot)
    d.meter = 2
    print(d.meter,d.foot)